Researchers and doctors made advances in battling Ebola and treating other deadly viruses in 2014, but the fight against other diseases — those treated with antibiotics — suffered a major setback.

Throughout the year, health workers labored to care for Ebola patients in West Africa while scientists fast-tracked treatments and anti-Ebola vaccines. Some are already in clinical trials. Others will be in early 2015.

The number of new infections is slowing, but until that number gets to zero, the disease could come raging back.

In April, the World Health Organization warned that the world was entering a "post-antibiotic era" in which there are no longer effective treatments for common but serious bacterial diseases. The U.S. Centers for Disease Control and Prevention said development had resulted in 23,000 deaths in the U.S. alone.

“You all of a sudden understand what it was like to practice medicine maybe 50, 70, 80 years ago, when there weren’t antibiotics,” said Dr. Trish Perl, an epidemiologist with Johns Hopkins Medicine.

The WHO is urging doctors to build a data pool on which antibiotics kill which strains of bacteria and to avoid prescribing antibiotics that aren't going to work.

Progress in fighting malaria was a highlight in 2014. Since 2000, the WHO reported, the number of cases has dropped by 47 percent.

"We are making steady progress," said Dr. Pedro Alonso, director of the WHO malaria program. "In fact, I would call it unprecedented progress in the fight against malaria."

The progress was made largely because people at risk for malaria were being given bed nets treated with insecticide. Testing and treatment were factors, too.

Alonso estimated that more than 4 million lives were saved — good news, especially for children, who account for malaria's greatest number of victims. But as always, there's more work to be done.

There was also promising research in developing a vaccine to combat dengue, another disease caused by a parasite that is transmitted by a mosquito. Dengue is 30 times more prevalent now than it was 50 years ago, according to the WHO.

In July, the French pharmaceutical company Sanofi Pasteur announced that its trials in Asian countries would enable it to develop a vaccine.

There are four strains of dengue, and a vaccine that might work on one strain may not work on others.

But British scientists have discovered molecules — specifically, antibodies — in human blood that stop all forms of dengue. The scientists said the molecules offer a road map for developing a simple vaccine that could be effective for all strains of the virus.